Magnetic sensor

ABSTRACT

A magnetic sensor includes an MR element and a support member. The support member has an opposed surface including a first inclined portion, and a bottom surface. In a given cross section, the first inclined portion is inclined at a first angle at a first position, and inclined at a second angle smaller than the first angle at a second position. The absolute value of a curvature of the first inclined portion at the first position is less than the absolute value of the curvature of the first inclined portion at the second position. The MR element is provided on the first inclined portion so that the first edge is located above the first position in a given cross section.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority PatentApplication No. 2021-009817 filed on Jan. 25, 2021, the entire contentsof which are incorporated herein by reference.

BACKGROUND

The technology relates to a magnetic sensor including a magnetoresistiveelement.

Magnetic sensors using magnetoresistive elements have been used forvarious applications in recent years. A system including a magneticsensor may be intended to detect a magnetic field containing a componentin a direction perpendicular to the surface of a substrate by using amagnetoresistive element provided on the substrate. In such a case, themagnetic field containing the component in the direction perpendicularto the surface of the substrate can be detected by providing a softmagnetic body for converting a magnetic field in the directionperpendicular to the surface of the substrate into a magnetic field inthe direction parallel to the surface of the substrate or locating themagnetoresistive element on an inclined surface formed on the substrate.

US 2008/0169807 A1 discloses first and second magnetic sensors eachincluding an X-axis sensor, a Y-axis sensor, and a Z-axis sensordisposed on a substrate. The first magnetic sensor has V-shaped groovesin a thick film located on its substrate. Band-like portions of giantmagnetoresistive elements constituting the Z-axis sensor are disposed atlocations having favorable flatness in the centers of the inclinedsurfaces of the grooves. The band-like portions are portionsconstituting the main bodies of the giant magnetoresistive elements andhave a long slender band-like planar shape.

The second magnetic sensor has V-shaped grooves each having a firstinclined surface and a second inclined surface in thick films located onits substrate. The second inclined surface constitutes a lower half ofthe inclined surface of the groove. An angle that the second inclinedsurface forms with the substrate is greater than an angle that the firstinclined surface forms with the substrate. Band-like portions of giantmagnetoresistive elements constituting the Z-axis sensor are disposed atlocations having favorable flatness in the centers of the secondinclined surfaces. The band-like portions have a long slender band-likeplanar shape.

US 2008/0169807 A1 describes the fact that the inclined surface isactually formed as a curved surface somewhat bulging out because of themanufacturing process.

A magnetoresistive element is typically formed by etching a layered filmto be the magnetoresistive element by ion milling or reactive ionetching. This etching process uses a photoresist mask. The photoresistmask is formed at a desired position on the layered film by usingphotolithography. The photoresist mask has a planar shape correspondingto that of the magnetoresistive element. However, the position anddimensions of the photoresist mask can vary due to the precision of thephotolithography.

The effect of variations in the position and dimensions of thephotoresist mask appear evidently in forming the magnetoresistiveelement on a curved surface. To form the magnetoresistive element on acurved surface, the layered film is typically formed in the shape of thecurved surface by using a so-called non-conformal film formationapparatus such as a magnetron sputtering apparatus. The thickness(dimension in a direction perpendicular to the curved surface) of thelayered film thus decreases as the inclination angle of the curvedsurface increases.

Suppose that the curved surface is shaped to bulge out. The amount ofchange in the inclination angle when the position on the curved surfacechanges horizontally by a predetermined distance increases withincreasing distance from the top of the curved surface. Similarly, theamount of change in the thickness of the layered film increases withincreasing distance from the top of the curved surface. If the positionor dimensions of the photoresist mask vary to change the position of awall surface of the photoresist mask on a side opposite from the top ofthe curved surface, the thickness of the magnetoresistive elementchanges greatly near the edge of the magnetoresistive element located onthe side opposite from the top of the curved surface. This gives rise toa problem that the desired characteristic is not obtained.

The foregoing problem also arises if the magnetoresistive element isformed on a curved surface of a recessed shape.

SUMMARY

A magnetic sensor according to one embodiment of the technology includesa magnetoresistive element whose resistance changes with an externalmagnetic field, and a support member configured to support themagnetoresistive element. The support member has an opposed surfaceopposed to the magnetoresistive element, and a bottom surface formed ofa flat surface located opposite the opposed surface. The opposed surfaceincludes an inclined portion inclined relative to the bottom surface. Ina specific cross section of the magnetic sensor perpendicular to thebottom surface, the inclined portion is inclined relative to the bottomsurface at a first angle at a first position on the inclined portion,and inclined relative to the bottom surface at a second angle at asecond position on the inclined portion, the second angle being smallerthan the first angle.

An absolute value of a curvature of the inclined portion at the firstposition is less than an absolute value of a curvature of the inclinedportion at the second position. The magnetoresistive element has a firstedge and a second edge located at both ends of the magnetoresistiveelement in a width direction, and is provided on the inclined portion sothat the first edge is located above the first position in the crosssection.

In the magnetic sensor according to one embodiment of the technology,the magnetoresistive element may be provided on the inclined portion sothat the second edge is located above the second position in the crosssection.

In the magnetic sensor according to one embodiment of the technology,the first position and the second position may fall within a range froma third position on the inclined portion closest to the bottom surfacein the cross section to a fourth position on the inclined portionfarthest from the bottom surface in the cross section. In such a case,the inclined portion may be inclined relative to the bottom surface sothat the first angle is a maximum and the second angle is a minimumwithin a range from the first position to the second position. Theabsolute value of the curvature of the inclined portion may be minimizedat the first position and maximized at a predetermined position otherthan the first position within the range from the first position to thesecond position.

In the magnetic sensor according to one embodiment of the technology,the opposed surface may include a convex surface protruding in adirection away from the bottom surface. In such a case, the inclinedportion may be a part of the convex surface. Alternatively, the opposedsurface may include a concave surface recessed toward the bottomsurface. In such a case, the inclined portion may be a part of theconcave surface.

In the magnetic sensor according to one embodiment of the technology,the magnetoresistive element may include a magnetic layer having amagnetization whose direction is variable depending on the externalmagnetic field. The magnetic layer may have a first surface and a secondsurface located opposite the first surface, and have a thickness that isa dimension in a direction perpendicular to the first surface of themagnetic layer. The thickness at the first edge may be smaller than thethickness at the second edge. The thickness may decrease toward thefirst edge from the second edge. The first surface and the secondsurface may each have a shape long in a direction intersecting the crosssection.

In the magnetic sensor according to one embodiment of the technology,the inclined portion of the opposed surface of the support member isinclined relative to the bottom surface at the first angle at the firstposition, and inclined relative to the bottom surface at the secondangle smaller than the first angle at the second position. The absolutevalue of the curvature of the inclined portion at the first position isless than that of the curvature of the inclined portion at the secondposition. The magnetoresistive element is provided on the inclinedportion so that the first edge is located above the first position.According to one embodiment of the technology, a change in the thicknessof the magnetoresistive element due to variations in the manufacturingprocess can thereby be reduced.

Other and further objects, features and advantages of the technologywill appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification. The drawings illustrate example embodimentsand, together with the specification, serve to explain the principles ofthe technology.

FIG. 1 is an explanatory diagram showing a schematic configuration of amagnetic sensor system of a first example embodiment of the technology.

FIG. 2 is a circuit diagram showing the circuit configuration of amagnetic sensor according to the first example embodiment of thetechnology.

FIG. 3 is a schematic diagram showing a part of the magnetic sensoraccording to the first example embodiment of the technology.

FIG. 4 is a cross-sectional view showing a part of the magnetic sensoraccording to the first example embodiment of the technology.

FIG. 5 is a plan view showing a part of the magnetic sensor according tothe first example embodiment of the technology.

FIG. 6 is a cross-sectional view showing a magnetoresistive element ofthe first example embodiment of the technology.

FIG. 7 is an explanatory diagram for describing a shape of an inclinedportion of the first example embodiment of the technology.

FIG. 8 is a cross-sectional view showing a step of a manufacturingmethod for the magnetic sensor according to the first example embodimentof the technology.

FIG. 9 is a cross-sectional view showing a step that follows the step inFIG. 8.

FIG. 10 is a cross-sectional view showing a step that follows the stepin FIG. 9.

FIG. 11 is a cross-sectional view showing a step that follows the stepin FIG. 10.

FIG. 12 is a cross-sectional view showing a step that follows the stepin FIG. 11.

FIG. 13 is a characteristic chart showing the shape and curvature of theopposed surface of the support member according to the first exampleembodiment of the technology.

FIG. 14 is an explanatory diagram for describing magnetic charges on amagnetoresistive element of a comparative example.

FIG. 15 is an explanatory diagram for describing magnetic charges on themagnetoresistive element of the first example embodiment of thetechnology.

FIG. 16 is a cross-sectional view showing a modification example of themagnetoresistive element of the first example embodiment of thetechnology.

FIG. 17 is a cross-sectional view showing a cross section of a magneticsensor according to a second example embodiment of the technology.

FIG. 18 is an explanatory diagram for describing a shape of an inclinedportion of the second example embodiment of the technology.

DETAILED DESCRIPTION

An object of the technology is to provide a magnetic sensor configuredso that a change in the thickness of a magnetoresistive element locatedon an inclined portion due to variations in the manufacturing processcan be reduced.

In the following, some example embodiments and modification examples ofthe technology are described in detail with reference to theaccompanying drawings. Note that the following description is directedto illustrative examples of the disclosure and not to be construed aslimiting the technology. Factors including, without limitation,numerical values, shapes, materials, components, positions of thecomponents, and how the components are coupled to each other areillustrative only and not to be construed as limiting the technology.Further, elements in the following example embodiments which are notrecited in a most-generic independent claim of the disclosure areoptional and may be provided on an as-needed basis. The drawings areschematic and are not intended to be drawn to scale. Like elements aredenoted with the same reference numerals to avoid redundantdescriptions. Note that the description is given in the following order.

First Example Embodiment

Example embodiments of the technology will now be described in detailwith reference to the drawings. An outline of a magnetic sensor systemincluding a magnetic sensor according to a first example embodiment ofthe technology will initially be described with reference to FIG. 1. Amagnetic sensor system 100 according to the present example embodimentincludes a magnetic sensor 1 according to the present example embodimentand a magnetic field generator 5. The magnetic field generator 5generates a target magnetic field MF that is a magnetic field for themagnetic sensor 1 to detect (magnetic field to be detected).

The magnetic field generator 5 is rotatable about a rotation axis C. Themagnetic field generator 5 includes a pair of magnets 6A and 6B. Themagnets 6A and 6B are arranged at symmetrical positions with a virtualplane including the rotation axis C at the center. The magnets 6A and 6Beach have an N pole and an S pole. The magnets 6A and 6B are located inan orientation such that the N pole of the magnet 6A is opposed to the Spole of the magnet 6B. The magnetic field generator 5 generates thetarget magnetic field MF in the direction from the N pole of the magnet6A to the S pole of the magnet 6B.

The magnetic sensor 1 is located at a position where the target magneticfield MF at a predetermined reference position can be detected. Thetarget magnetic field MF at the reference position is part of themagnetic fields generated by the respective magnets 6A and 6B. Thereference position may be located on the rotation axis C. In thefollowing description, the reference position is located on the rotationaxis C. The magnetic sensor 1 detects the target magnetic field MFgenerated by the magnetic field generator 5, and generates a detectionvalue Vs. The detection value Vs has a correspondence with a relativeposition, or rotational position in particular, of the magnetic fieldgenerator 5 with respect to the magnetic sensor 1.

The magnetic sensor system 100 can be used as a device for detecting therotational position of a rotatable moving part in an apparatus thatincludes the moving part. Examples of such an apparatus include a jointof an industrial robot. FIG. 1 shows an example where the magneticsensor system 100 is applied to an industrial robot 200.

The industrial robot 200 shown in FIG. 1 includes a moving part 201 anda support unit 202 that rotatably supports the moving part 201. Themoving part 201 and the support unit 202 are connected at a joint. Themoving part 201 rotates about the rotation axis C. For example, if themagnetic sensor system 100 is applied to the joint of the industrialrobot 200, the magnetic sensor 1 may be fixed to the support unit 202,and the magnets 6A and 6B may be fixed to the moving part 201.

Now, we define X, Y, and Z directions as shown in FIG. 1. The X, Y, andZ directions are orthogonal to one another. In the present exampleembodiment, a direction parallel to the rotation axis C (in FIG. 1, adirection out of the plane of the drawing) will be referred to as the Xdirection. In FIG. 1, the Y direction is shown as a rightward direction,and the Z direction is shown as an upward direction. The oppositedirections to the X, Y, and Z directions will be referred to as −X, −Y,and −Z directions, respectively. As used herein, the term “above” refersto positions located forward of a reference position in the Z direction,and “below” refers to positions located on a side of the referenceposition opposite to “above”.

In the present example embodiment, the direction of the target magneticfield MF at the reference position is expressed as a direction withinthe YZ plane including the reference position on the rotation axis C.The direction of the target magnetic field MF at the reference positionrotates about the reference position within the foregoing YZ plane.

The magnetic sensor 1 includes magnetoresistive elements (hereinafter,referred to as MR elements) whose resistances change with an externalmagnetic field. In the present example embodiment, the resistances ofthe MR elements change with a change in the direction of the targetmagnetic field MF. The magnetic sensor 1 generates detection signalscorresponding to the resistances of the MR elements, and generates adetection value Vs based on the detection signals.

Next, a configuration of the magnetic sensor 1 according to the presentexample embodiment will be described. An example of a circuitconfiguration of the magnetic sensor 1 will initially be described withreference to FIG. 2. In the example shown in FIG. 2, the magnetic sensor1 includes four resistor sections 11, 12, 13, and 14, two power supplynodes V1 and V2, two ground nodes G1 and G2, and two signal output nodesE1 and E2.

The resistor sections 11 to 14 each include at least one MR element 30.If each of the resistor sections 11 to 14 includes a plurality of MRelements 30, the plurality of MR elements 30 in each of the resistorsections 11 to 14 may be connected in series.

The resistor section 11 is provided between the power supply node V1 andthe signal output node E1. The resistor section 12 is provided betweenthe signal output node E1 and the ground node G1. The resistor section13 is provided between the power supply node V2 and the signal outputnode E2. The resistor section 14 is provided between the signal outputnode E2 and the ground node G2. The power supply nodes V1 and V2 areconfigured to receive a power supply voltage of predetermined magnitude.The ground nodes G1 and G2 are connected to the ground.

The potential of the connection point between the resistor section 11and the resistor section 12 changes depending on the resistance of theat least one MR element 30 of the resistor section 11 and the resistanceof the at least one MR element 30 of the resistor section 12. The signaloutput node E1 outputs a signal corresponding to the potential of theconnection point between the resistor section 11 and the resistorsection 12 as a detection signal S1.

The potential of the connection point between the resistor section 13and the resistor section 14 changes depending on the resistance of theat least one MR element 30 of the resistor section 13 and the resistanceof the at least one MR element 30 of the resistor section 14. The signaloutput node E2 outputs a signal corresponding to the potential of theconnection point between the resistor section 13 and the resistorsection 14 as a detection signal S2.

The magnetic sensor 1 further includes a detection value generationcircuit 21 that generates the detection value Vs on the basis of thedetection signals S1 and S2. The detection value generation circuit 21includes an application specific integrated circuit (ASIC) or amicrocomputer, for example.

Next, the configuration of the magnetic sensor 1 will be described inmore detail with attention focused on one MR element 30. FIG. 3 is aschematic diagram showing a part of the magnetic sensor 1. FIG. 4 is across-sectional view showing a part of the magnetic sensor 1. FIG. 4shows a cross section parallel to the YZ plane and intersecting the MRelement 30. FIG. 5 is a plan view showing a part of the magnetic sensor1.

The magnetic sensor 1 further includes a support member 60. The supportmember 60 supports all the MR elements 30 included in the resistorsections 11 to 14. As shown in FIGS. 3 and 4, the support member 60includes an opposed surface 60 a opposed, at least in part, to the MRelements 30, and a bottom surface 60 b formed of a flat surface locatedopposite the opposed surface 60 a. The opposed surface 60 a is locatedat an end of the support member 60 in the Z direction. The bottomsurface 60 b is located at an end of the support member 60 in the −Zdirection. The bottom surface 60 b is parallel to the XY plane. Forexample, the magnetic sensor 1 may be manufactured with the bottomsurface 60 b or a surface corresponding to the bottom surface 60 b madehorizontal. For example, the magnetic sensor 1 may be installed based onthe direction or tilt of the bottom surface 60 b or the surfacecorresponding to the bottom surface 60 b. The bottom surface 60 b maythus serve as a reference plane in at least either the manufacturing orthe installing of the magnetic sensor 1.

The opposed surface 60 a of the support member 60 includes an inclinedportion inclined relative to the bottom surface 60 b. In the presentexample embodiment, the opposed surface 60 a includes a flat portion 60a 1 parallel to the bottom surface 60 b and at least one curved portion60 a 2 not parallel to the bottom surface 60 b. As shown in FIG. 4, thecurved portion 60 a 2 is a convex surface protruding in a direction awayfrom the bottom surface 60 b. The foregoing inclined portion is a partof the convex surface. The curved portion 60 a 2 has a curved shape(arch shape) curved to protrude in a direction away from the bottomsurface 60 b (Z direction) in a given cross section parallel to the YZplane. In a given cross section parallel to the YZ plane, the distancefrom the bottom surface 60 b to the curved portion 60 a 2 is maximizedat the center of the curved portion 60 a 2 in a direction parallel tothe Y direction (hereinafter, referred to simply as the center of thecurved portion 60 a 2).

The curved portion 60 a 2 extends along the X direction. As shown inFIG. 3, the overall shape of the curved portion 60 a 2 is asemicylindrical curved surface formed by moving the curved shape (archshape) shown in FIG. 4 along the X direction.

The MR element 30 is located on the curved portion 60 a 2. A portion ofthe curved portion 60 a 2 from an edge at the end of the curved portion60 a 2 in the −Y direction to the center of the curved portion 60 a 2will be referred to as a first inclined portion and be denoted by thesymbol SL1. A portion of the curved portion 60 a 2 from an edge at theend of the curved portion 60 a 2 in the Y direction to the center of thecurved portion 60 a 2 will be referred to as a second inclined portionand be denoted by the symbol SL2. In FIG. 3, the border between thefirst inclined portion SL1 and the second inclined portion SL2 is shownby a dotted line. Both the first and second inclined portions SL1 andSL2 are inclined relative to the bottom surface 60 b. In the presentexample embodiment, the entire MR element 30 is located on the firstinclined portion SL1 or the second inclined portion SL2. FIGS. 3 and 4show the MR element 30 located on the first inclined portion SL1.

The MR element 30 has a shape that is long in the X direction. Asemployed herein, the lateral direction of the MR element 30 will bereferred to as the width direction of the MR element 30 or simply as thewidth direction. The MR element 30 may have a planar shape (shape seenin the Z direction), like a rectangle, including a constant widthportion having a constant or substantially constant width in the widthdirection regardless of the position in the X direction. The MR element30 may have a planar shape including no constant width portion, like anellipse. Examples of the planar shape of the MR element 30 including aconstant width portion include a rectangular shape where bothlongitudinal ends are straight, an oval shape where both longitudinalends are semicircular, and a shape where both longitudinal ends arepolygonal. FIGS. 3 and 5 show the case where the MR element 30 has arectangular planar shape. In this example, the MR element 30 has abottom surface 30 a, a top surface 30 b, a first edge 30 c, a secondedge 30 d, a third edge 30 e, and a fourth edge 30 f. The bottom surface30 a is opposed to the curved portion 60 a 2. The top surface 30 b islocated opposite the bottom surface 30 a. The first and second edges 30c and 30 d are located at both ends in the width direction. The thirdand fourth edges 30 e and 30 f are located at both ends in thelongitudinal direction. The dimension of the MR element 30 in the widthdirection is constant or substantially constant regardless of theposition in the X direction.

The support member 60 includes a substrate 61 and an insulating layer 62located on the substrate 61. The substrate 61 is a semiconductorsubstrate made of a semiconductor such as Si, for example. The substrate61 has a top surface located at an end of the substrate 61 in the Zdirection, and a bottom surface located at an end of the substrate 61 inthe −Z direction. The bottom surface 60 b of the support member 60 isconstituted by the bottom surface of the substrate 61. The substrate 61has a constant thickness (dimension in the Z direction).

The insulating layer 62 is made of an insulating material such as SiO₂,for example. The insulating layer 62 includes a top surface located atan end in the Z direction. The opposed surface 60 a of the supportmember 60 is constituted by the top surface of the insulating layer 62.The insulating layer 62 has a cross-sectional shape such that the curvedportion 60 a 2 is formed on the opposed surface 60 a. Specifically, theinsulating layer 62 has a cross-sectional shape of bulging out in the Zdirection in a given cross section parallel to the YZ plane.

The magnetic sensor 1 further includes a lower electrode 41, an upperelectrode 42, and insulating layers 63, 64 and 65. In FIG. 3, the lowerelectrode 41, the upper electrode 42, and the insulating layers 63 to 65are omitted. In FIG. 5, the insulating layers 63 to 65 are omitted.

The lower electrode 41 is located on the opposed surface 60 a of thesupport member 60 (the top surface of the insulating layer 62). Theinsulating layer 63 is located on the opposed surface 60 a of thesupport member 60, around the lower electrode 41. The MR element 30 islocated on the lower electrode 41. The insulating layer 64 is located onthe lower electrode 41 and the insulating layer 63, around the MRelement 30. The upper electrode 42 is located on the MR element 30 andthe insulating layer 64. The insulating layer 65 is located on theinsulating layer 64, around the upper electrode 42.

The magnetic sensor 1 further includes a not-shown insulating layercovering the upper electrode 42 and the insulating layer 65. The lowerelectrode 41 and the upper electrode 42 are made of a conductivematerial such as Cu, for example. The insulating layers 63 to 65 and thenot-shown insulating layer are made of an insulating material such asSiO₂, for example.

The substrate 61 and the portions of the magnetic sensor 1 stacked onthe substrate 61 are referred to collectively as a detection unit. FIG.4 can be said to show the detection unit. The detection value generationcircuit 21 shown in FIG. 2 may be integrated with or separate from thedetection unit.

Now, the configuration of the MR element 30 will be described in detailwith reference to FIG. 6. In particular, in the present exampleembodiment, the MR element 30 is a spin-valve MR element. As shown inFIG. 6, the MR element 30 includes a magnetization pinned layer 32having a magnetization whose direction is fixed, a free layer 34 havinga magnetization whose direction is variable depending on the directionof an external magnetic field, and a spacer layer 33 located between themagnetization pinned layer 32 and the free layer 34. The MR element 30may be a tunneling magnetoresistive (TMR) element or a giantmagnetoresistive (GMR) element. In the TMR element, the spacer layer 33is a tunnel barrier layer. In the GMR element, the spacer layer 33 is anonmagnetic conductive layer. The resistance of the MR element 30changes with an angle that the direction of the magnetization of thefree layer 34 forms with respect to the direction of the magnetizationof the magnetization pinned layer 32. The resistance is minimized if theangle is 0°. The resistance is maximized if the angle is 180°.

The magnetization pinned layer 32, the spacer layer 33, and the freelayer 34 are stacked in this order from the lower electrode 41 in thedirection toward the upper electrode 42. The MR element 30 furtherincludes an underlayer 31 interposed between the magnetization pinnedlayer 32 and the lower electrode 41, and a cap layer 35 interposedbetween the free layer 34 and the upper electrode 42. The arrangement ofthe magnetization pinned layer 32, the spacer layer 33, and the freelayer 34 in the MR element 30 may be vertically reversed from that shownin FIG. 6.

The direction of the magnetization of the magnetization pinned layer 32is desirably orthogonal to the longitudinal direction of the MR element30. In the present example embodiment, the MR element 30 is located onthe first inclined portion SL1 or the second inclined portion SL2inclined relative to the bottom surface 60 b. The direction of themagnetization of the magnetization pinned layer 32 is thus also inclinedrelative to the bottom surface 60 b.

For the sake of convenience, in the present example embodiment, thedirection of the magnetization of the magnetization pinned layer 32located on the first inclined portion SL1 will be referred to as a Udirection or a −U direction. The U direction is a direction rotated fromthe Y direction toward the Z direction by a predetermined angle. The −Udirection is the direction opposite to the U direction. For the sake ofconvenience, in the present example embodiment, the direction of themagnetization of the magnetization pinned layer 32 located on the secondinclined portion SL2 will be referred to as a V direction or a −Vdirection. The V direction is a direction rotated from the Y directiontoward the −Z direction by a predetermined angle. The −V direction isthe direction opposite to the V direction.

The X, U, and V directions are shown in FIG. 2. For the sake ofconvenience, in FIG. 2, the U direction and the V direction areindicated by the same arrow. In FIG. 2, the filled arrows indicate thedirections of the magnetizations of the magnetization pinned layers 32of the MR elements 30 included in the respective resistor sections 11 to14. The magnetic sensor 1 may be configured so that the directions ofthe magnetizations of the magnetization pinned layers 32 of the MRelements 30 in the resistor sections 11 and 14 are the U direction, andthe directions of the magnetizations of the magnetization pinned layers32 of the MR elements 30 in the resistor sections 12 and 13 are the −Udirection. Alternatively, the magnetic sensor 1 may be configured sothat the directions of the magnetizations of the magnetization pinnedlayers 32 of the MR elements 30 in the resistor sections 11 and 14 arethe V direction, and the directions of the magnetizations of themagnetization pinned layers 32 of the MR elements 30 in the resistorsections 12 and 13 are the −V direction.

Alternatively, the magnetic sensor 1 may include a first circuit portionand a second circuit portion each including the resistor sections 11 to14. The first circuit portion may be configured so that the directionsof the magnetizations of the magnetization pinned layers 32 of the MRelements 30 in the resistor sections 11 and 14 are the U direction, andthe directions of the magnetizations of the magnetization pinned layers32 of the MR elements 30 in the resistor sections 12 and 13 are the −Udirection. The second circuit portion may be configured so that thedirections of the magnetizations of the magnetization pinned layers 32of the MR elements 30 in the resistor sections 11 and 14 are the Vdirection, and the directions of the magnetizations of the magnetizationpinned layers 32 of the MR elements 30 in the resistor sections 12 and13 are the −V direction.

The free layer 34 corresponds to a magnetic layer according to thetechnology. The free layer 34 has magnetic shape anisotropy where thedirection of the easy axis of magnetization intersects the direction ofthe magnetization of the magnetization pinned layer 32. In the presentexample embodiment, the MR element 30 is patterned to a shape that islong in the X direction. This gives the free layer 34 magnetic shapeanisotropy where the direction of the easy axis of magnetization isparallel to the X direction.

Up to this point, the configuration of the magnetic sensor 1 has beendescribed with attention focused on one MR element 30. In the presentexample embodiment, the resistor sections 11 to 14 each include at leastone MR element 30. The magnetic sensor 1 thus includes a plurality of MRelements 30, a plurality of lower electrodes 41, and a plurality ofupper electrodes 42. As shown in FIG. 5, each of the lower electrodes 41has a long slender shape. The MR element 30 is provided on the topsurface of the lower electrode 41, near one end in the longitudinaldirection. Each upper electrode 42 has a long slender shape and islocated over two lower electrodes 41 to electrically connect twoadjoining MR elements 30.

The number of the curved portions 60 a 2 of the opposed surface 60 a ofthe support member 60 may be one or more than one. If the number of thecurved portions 60 a 2 is one, the plurality of MR elements 30 arelocated on the one curved portion 60 a 2. In such a case, the pluralityof MR elements 30 may be located on either one of the first and secondinclined portions SL1 and SL2 or on both the first and second inclinedportions SL1 and SL2.

If the number of curved portions 60 a 2 is more than one, one or aplurality of MR elements 30 may be located on one curved portion 60 a 2.In such a case, the plurality of curved portions 60 a 2 may be arrangedalong one direction. Alternatively, the plurality of curved portions 60a 2 may be arranged in a plurality of rows, i.e., more than one curvedportion 60 a 2 in both the X and Y directions.

Next, the inclined portions and the MR elements 30 will be described inmore detail with reference to FIGS. 6 and 7. The following descriptionwill be given by using the first inclined portion SL1 as an example.FIG. 7 is an explanatory diagram for describing the shape of the firstinclined portion SL1. In FIG. 7, the underlayer 31 and the cap layer 35of the MR element 30 are omitted.

FIG. 7 shows a specific cross section intersecting the MR element 30 andbeing perpendicular to the bottom surface 60 b of the support member 60.Such a cross section will hereinafter be denoted by the symbol S. Thecross section S intersects the longitudinal direction of the MR element30. To describe the shape of the first inclined portion SL1, a firstposition P1, a second position P2, a third position P3, and a fourthposition P4 on the first inclined portion SL1 in a given cross section Swill be defined as follows. The first position P1 is a position wherethe first inclined portion SL1 is inclined relative to the bottomsurface 60 b at a first angle θ1. The second position P2 is a positionwhere the first inclined portion SL1 is inclined relative to the bottomsurface 60 b at a second angle θ2 smaller than the first angle θ1. Inthe present example embodiment, in particular, the first position P1 iscloser to the bottom surface 60 b than is the second position P2. In thefollowing description, the angle that a specific surface forms with thebottom surface 60 b will be expressed in terms of an angle of 0° or moreand not more than 90°.

The third position P3 is the position on the first inclined portion SL1closest to the bottom surface 60 b. Specifically, the third position P3refers to the end of the first inclined portion SL1 in the −Y direction,and is located at the border between the curved portion 60 a 2 and theflat portion 60 a 1. The fourth position P4 is the position on the firstinclined portion SL1 farthest from the bottom surface 60 b.Specifically, the fourth position P4 refers to the end of the firstinclined portion SL1 in the Y direction, and is located at the borderbetween the first inclined portion SL1 and the second inclined portionSL2, i.e., the center of the curved portion 60 a 2. The first positionP1 and the second position P2 fall within the range from the thirdposition P3 to the fourth position P4.

Both the angle that the first inclined portion SL1 forms with the bottomsurface 60 b at the third position P3 and the angle that the firstinclined portion SL1 forms with the bottom surface 60 b at the fourthposition P4 are 0°. Both the first and second angles θ1 and 02 aregreater than 0° and less than 90°. In the present example embodiment, inparticular, the first inclined portion SL1 is inclined relative to thebottom surface 60 b so that the first angle θ1 is maximum and the secondangle θ2 is minimum within the range from the first position P1 to thesecond position P2.

The outline of the first inclined portion SL1 in a given cross section Sincludes a plurality of curves where each curve has a differentcurvature. The absolute value of a curvature k1 of the first inclinedportion SL1 at the first position P1 is less than that of a curvature k2of the first inclined portion SL1 at the second position P2. In otherwords, the first inclined portion SL1 at the first position P1 isstraighter than the first inclined portion SL1 at the second positionP2, and curves gently.

In FIG. 7, the circular arc denoted by the symbol C1 represents a partof a circle approximating the first inclined portion SL1 at the firstposition P1, i.e., a first circle of curvature. The circular arc denotedby the symbol C2 represents a part of a circle approximating the firstinclined portion SL1 at the second position P2, i.e., a second circle ofcurvature. As shown in FIG. 7, the first circle of curvature (symbol C1)has a radius greater than that of the second circle of curvature (symbolC2).

In the range from the first position P1 to the second position P2, theabsolute value of the curvature of the first inclined portion SL1 ismaximized at a predetermined position other than the first position P1on the first inclined portion SL1. The predetermined position may be thesecond position P2 or a position other than the first and secondpositions P1 and P2. The absolute value of the curvature of the firstinclined portion SL1 may increase monotonically from the first positionP1 to the second position P2, or may increase on a whole whileincreasing and decreasing repeatedly.

In the example shown in FIG. 7, the outline of the first inclinedportion SL1 in a given cross section S is a smooth curve from the firstposition P1 to the second position P2. However, the outline of the firstinclined portion SL1 may include a point where the curvature issubstantially infinite. In such a case, the outline of the firstinclined portion SL1 bends at the point where the curvature issubstantially infinite. An angle θb that the first inclined portion SL1forms with the bottom surface 60 b at the bending point is defined asfollows. An angle that the first inclined portion SL1 forms with thebottom surface 60 b at a point on the first inclined portion SL1 nearthe bending point and closer to the bottom surface 60 b than is thebending point will be denoted by θa. An angle that the first inclinedportion SL1 forms with the bottom surface 60 b at a point on the firstinclined portion SL1 near the bending point and farther from the bottomsurface 60 b than is the bending point will be denoted by θc. The angleθb is an angle smaller than the angle θa and greater than the angle θc.The angle θb may be an average of the angles θa and θc.

The MR element 30 is provided on the first inclined portion SL1 so thatthe first edge 30 c is located above the first position P1 in a givencross section S. Further, in the present example embodiment, the MRelement 30 is provided on the first inclined portion SL1 so that thesecond edge 30 d is located above the second position P2 in the givencross section S. Thus, in the present example embodiment, the MR element30 is provided on the area ranging from the first position P1 to thesecond position P2 on the first inclined portion SL1.

As shown in FIGS. 6 and 7, the free layer 34 of the MR element 30includes a first surface 34 a, a second surface 34 b opposite to thefirst surface 34 a, and an outer peripheral surface connecting the firstsurface 34 a and the second surface 34 b. The first surface 34 a islocated farther from the opposed surface 60 a of the support member 60than is the second surface 34 b. The first surface 34 a is in contactwith the cap layer 35. The second surface 34 b is in contact with thespacer layer 33.

In the present example embodiment, the MR element 30 is patterned to ashape that is long in the X direction. The first and second surfaces 34a and 34 b thus each have a shape that is long in the X direction. Thefirst surface 34 a has a first edge Ed1 and a second edge Ed2 located atboth lateral ends of the first surface 34 a. The first edge Ed1 islocated at the first edge 30 c of the MR element 30. The second edge Ed2is located at the second edge 30 d of the MR element 30.

As employed herein, an angle that the first surface 34 a forms with thebottom surface 60 b of the support member 60 will be referred to as aninclination angle and denoted by the symbol ϕ. The first surface 34 a isinclined relative to the bottom surface 60 b of the support member 60 sothat the inclination angle ϕ is greater than 0°.

As employed herein, the inclination angle ϕ at the first edge Ed1 willbe referred to as an inclination angle ϕ1. The inclination angle ϕ atthe second edge Ed2 will be referred to as an inclination angle ϕ2. In agiven cross section S, the inclination angle ϕ1 at the first edge Ed1 isgreater than the inclination angle ϕ2 at the second edge Ed2. In a givencross section S, the inclination angle ϕ may increase toward the firstedge Ed1 from the second edge Ed2.

The inclination angle ϕ at a given position on the first surface 34 achanges depending on the angle θ that the first inclination portion SL1forms with the bottom surface 60 b. Specifically, the inclination angleϕ at a given position on the first surface 34 a is substantially thesame as the angle θ at a position on the first inclined portion SL1below the given position. The inclination angle ϕ thus increases as theangle θ increases.

The free layer 34 has a thickness T that is a dimension in a directionperpendicular to the first surface 34 a. The thickness T can also besaid to be the distance between the first and second surfaces 34 a and34 b in the direction perpendicular to the first surface 34 a. Asemployed herein, the thickness T at the first edge Ed1 will be referredto as a thickness T1. The thickness T at the second edge Ed2 will bereferred to as a thickness T2. The thickness T1 is also the thickness Tat the first edge 30 c of the MR element 30. The thickness T2 is alsothe thickness T at the second edge 30 d of the MR element 30. For thesake of convenience, an imaginary surface is assumed by extending thesecond surface 34 b along the curved portion 60 a 2, and the thicknessT2 is defined as the distance between the first surface 34 a and theimaginary surface in the direction perpendicular to the first surface 34a.

In a given cross section S, the thickness T1 at the first edge Ed1 issmaller than the thickness T2 at the second edge Ed2. In a given crosssection S, the thickness T may decrease toward the first edge Ed1 fromthe second edge Ed2.

The thickness T at a given position on the first surface 34 a changesdepending on the angle θ. Specifically, the thickness T at a givenposition on the first surface 34 a decreases as the angle θ at theposition on the first inclined portion SL1 closest to the given positionincreases.

From the relationship between the inclination angle ϕ and the angle θand the relationship between the thickness T and the angle θ, thethickness T decreases as the inclination angle ϕ increases.

The foregoing description has been given by using the first inclinedportion SL1 as an example. The first inclined portion SL1 and the secondinclined portion SL2 have a shape symmetrical or substantiallysymmetrical about the XZ plane including the center of the curvedportion 60 a 2. The foregoing description of the first inclined portionSL1 therefore also applies to the second inclined portion SL2. Theforegoing description of the MR element 30 also applies to the MRelement 30 provided on the second inclined portion SL2.

Now, a manufacturing method for the magnetic sensor 1 according to thepresent example embodiment will be described with reference to FIG. 8 toFIG. 12. The manufacturing method for the magnetic sensor 1 includessteps of forming the portions of the magnetic sensor 1 shown in FIGS. 3to 5, i.e., the detection unit, and steps of completing the magneticsensor 1 by using the detection unit. FIGS. 8 to 12 show the steps offorming the detection unit. Note that FIGS. 8 to 12 deal with the MRelement 30 formed on the first inclined portion SL1.

As shown in FIG. 8, in the steps of forming the detection unit, theinsulating layer 62 is initially formed on the substrate 61. Theinsulating layer 62 may be formed by forming a photoresist mask on thesubstrate 61 and then forming an insulating film. The insulating layer62 may be formed by forming an insulating film on the substrate 61 andthen etching a part of the insulating film. The formation of theinsulating layer 62 completes the support member 60.

FIG. 9 shows the next step. In this step, the lower electrode 41 and theinsulating layer 63 are formed on the insulating layer 62, i.e., on thesupport member 60. For example, the lower electrode 41 and theinsulating layer 63 are formed in the following manner. A metal film isinitially formed on the insulating layer 62. An etching mask is thenformed on the metal film. The etching mask may be formed byphotolithographically patterning a photoresist layer. Next, the metalfilm is etched using the etching mask to be made into the lowerelectrode 41. The insulating layer 63 is then formed with the etchingmask left unremoved. The etching mask is then removed.

FIG. 10 shows the next step. In this step, films that later become thelayers constituting the MR element 30 are formed in order, and a layeredfilm 30P which later becomes the MR element 30 is formed on the lowerelectrode 41 and the insulating layer 63. An etching mask 81 is thenformed on the layered film 30P. The etching mask 81 is formed byphotolithographically patterning a photoresist layer. The etching mask81 has a planar shape (shape seen from above) corresponding to that ofthe MR element 30. The etching mask 81 has a first wall surface 81 a fordefining the position of the first edge 30 c of the MR element 30, and asecond wall surface 81 b for defining the position of the second edge 30d of the MR element 30.

FIG. 11 shows the next step. In this step, the layered film 30P isetched by, for example, ion milling or reactive ion etching using theetching mask 81. The layered film 30P is thereby made into the MRelement 30.

FIG. 12 shows the next step. In this step, the insulating layer 64 isinitially formed with the etching mask 81 left unremoved. The etchingmask 81 is then removed. The upper electrode 42 and the insulating layer65 are then formed on the MR element 30 and the insulating layer 64. Themethod for forming the upper electrode 42 and the insulating layer 65 isthe same as that for forming the lower electrode 41 and the insulatinglayer 63.

A not-shown insulating layer is then formed to cover the upper electrode42 and the insulating layer 65. Next, a plurality of terminalsconstituting the power supply nodes V1 and V2 and the like are formed tocomplete the detection unit of the magnetic sensor 1.

Next, an example of the shape and curvature of the opposed surface 60 aof the support member 60 will be described with reference to FIG. 13.FIG. 13 is a characteristic chart showing the shape and curvature of theopposed surface 60 a of the support member 60 in a predetermined crosssection S. FIG. 13 is obtained by measuring the opposed surface 60 a ofan actually manufactured support member 60 under an atomic forcemicroscope. In FIG. 13, the horizontal axis indicates the position in adirection parallel to the Y direction. The vertical axis on the leftindicates the curvature of the opposed surface 60 a. The curvature shownin FIG. 13 is defined so that the curvature has a positive value if theopposed surface 60 a is a convex surface protruding in a direction awayfrom the bottom surface 60 b. The vertical axis on the right indicatesthe height of the opposed surface 60 a. In FIG. 13, the height of theopposed surface 60 a refers to the position in a direction parallel tothe Z direction. In FIG. 13, the height of the flat portion 60 a 1 ofthe opposed surface 60 a is assumed to be 0. The solid line denoted bythe reference numeral 71 represents the curvature of the opposed surface60 a. The thick solid line denoted by the reference numeral 72represents the height of the opposed surface 60 a.

In FIG. 13, the points denoted by the symbols P1L and P2L represent thepositions corresponding to the first and second edges 30 c and 30 d ofthe MR element 30 provided on the first inclined portion SL1,respectively. The MR element 30 is provided on the area ranging from thepoint P1L to the point P2L on the first inclined portion SL1. The pointsP1L and P2L substantially represent the first and second positions P1and P2 on the first inclined portion SL1. As shown in FIG. 13, the anglethat the opposed surface 60 a forms with the bottom surface 60 b at thepoint P1L is greater than the angle that the opposed surface 60 a formswith the bottom surface 60 b at the point P2L. The absolute value of thecurvature of the opposed surface 60 a at the point P1L is less than thatof the curvature of the opposed surface 60 a at the point P2L. In therange from the point P1L to the point P2L, the absolute value of thecurvature of the opposed surface 60 a is minimized at the point P1L andmaximized at a predetermined position other than the point P1L.

Similarly, in FIG. 13, the points denoted by the symbols P1R and P2Rrepresent the positions corresponding to the first and second edges 30 cand 30 d of an MR element 30 provided on the second inclined portionSL2, respectively. The MR element 30 is provided on the area rangingfrom the point P1R to the point P2R on the second inclined portion SL2.The points P1R and P2R substantially represent the first and secondpositions P1 and P2 on the second inclined portion SL2. As shown in FIG.13, the angle that the opposed surface 60 a forms with the bottomsurface 60 b at the point P1R is greater than the angle that the opposedsurface 60 a forms with the bottom surface 60 b at the point P2R. Theabsolute value of the curvature of the opposed surface 60 a at the pointP1R is less than that of the curvature of the opposed surface 60 a atthe point P2R. In the range from the point P1R to the point P2R, theabsolute value of the curvature of the opposed surface 60 a is minimizedat the point P1R and maximized at a predetermined position other thanthe point P1R.

The operation and effect of the magnetic sensor 1 according to thepresent example embodiment will now be described. As shown in FIG. 7, inthe present example embodiment, the first inclined portion SL1 isinclined relative to the bottom surface 60 b at the first angle θ1 atthe first position P1 and inclined relative to the bottom surface 60 bat the second angle θ2 smaller than the first angle θ1 at the secondposition P2 in a given cross section S. The absolute value of thecurvature k1 of the first inclined portion SL1 at the first position P1is less than that of the curvature k2 of the first inclined portion SL1at the second position P2.

The MR element 30 provided on the first inclined portion SL1 is disposedon the first inclined portion SL1 so that the first edge 30 c is locatedabove the first position P1 in a given cross section S. Further, in thepresent example embodiment, the MR element 30 is disposed on the firstinclined portion SL1 so that the second edge 30 d is located above thesecond position P2 in the given cross section S.

As described with reference to FIGS. 8 to 12, the MR element 30 isformed by etching the layered film 30P. The etching uses the etchingmask 81. The etching mask 81 is formed at a desired position on thelayered film 30P by photolithographically patterning a photoresistlayer.

The etching mask 81 has the first wall surface 81 a for defining theposition of the first edge 30 c of the MR element 30 and the second wallsurface 81 b for defining the position of the second edge 30 d of the MRelement 30. The first wall surface 81 a is designed to be located abovethe first position P1 defined in advance. The second wall surface 81 bis designed to be located above the second position P2 defined inadvance. However, in the actual manufacturing process, the position anddimensions of the etching mask 81 can vary due to the precision of thephotolithography. This changes the positions of the first and secondwall surfaces 81 a and 81 b, and the positions of the first and secondedges 30 c and 30 d of the MR element 30 deviate from the respectivedesigned positions.

The amount of deviation in the angle that the first inclined portion SL1forms with the bottom surface 60 b at a predetermined position P on thefirst inclined portion SL1 will now be described. Here, the angle thatthe first inclined portion SL1 forms with the bottom surface 60 b at thepredetermined position P will be denoted by the symbol θ. The curvatureof the first inclined portion SL1 at the predetermined position P willbe denoted by the symbol k. The amount of deviation in the angle thatthe first inclined portion SL1 forms with the bottom surface 60 b whenthe predetermined position P is shifted by Δy in the direction parallelto the Y direction will be denoted by the symbol Δθ. If Δy issufficiently small, the amount of deviation Δθ can be expressed by thefollowing Eq. (1):

Δθ=k*Δy/cos θ  (1)

Here, the curvature k is assumed to be constant.

As can be seen from Eq. (1), the greater the curvature k, the greaterthe amount of deviation Δθ. The greater the angle θ, the greater theamount of deviation Δθ as well.

As described above, the thickness T of the free layer 34 of the MRelement 30 changes depending on the angle θ. Thus, from Eq. (1), it canbe said that the greater the curvature k, the greater the amount ofchange in the thickness T, and the greater the angle θ, the greater theamount of change in the thickness T.

In the present example embodiment, the first angle θ1 is greater thanthe second angle θ2. Suppose, for example, that the outline of the firstinclined portion SL1 has a constant curvature k like a circular arc, andgiven the same Δy, the amount of deviation Δθ near the first position P1is greater than the amount of deviation Δθ near the second position P2.As a result, the amount of change in the thickness T at the first edge30 c is greater than the amount of change in the thickness T at thesecond edge 30 d.

By contrast, in the present example embodiment, the absolute value ofthe curvature k1 of the first inclined portion SL1 at the first positionP1 is less than that of the curvature k2 of the first inclined portionSL1 at the second position P2. In other words, in the present exampleembodiment, the first inclined portion SL1 is configured to have arelatively small curvature k at the position where the amount of changein the thickness T of the free layer 34 is relatively large. As aresult, according to the present example embodiment, a change in thethickness T of the free layer 34 near the first edge 30 c due tovariations in the manufacturing process can thus be reduced compared tothe case where the curvature k of the first inclined portion SL1 isconstant or the absolute value of the curvature k1 is greater than thatof the curvature k2.

According to the present example embodiment, a change in the thicknessesof the layers constituting the MR element 30, other than the free layer34 near the first edge 30 c, due to variations in the manufacturingprocess can also be reduced. As a result, according to the presentexample embodiment, a change in the thickness of the MR element 30 (adimension in the direction perpendicular to the first inclined portionSL1) near the first edge 30 c due to variations in the manufacturingprocess can be reduced.

In the present example embodiment, the MR element 30 is provided so thatthe second edge 30 d is located above the second position P2 where theamount of change in the thickness T of the free layer 34 is relativelysmall. Therefore, according to the present example embodiment, a changein the thickness T of the free layer 34 near the second edge 30 d andthe thickness of the MR element 30 near the second edge 30 d due tovariations in the manufacturing process can thus be reduced. As aresult, according to the present example embodiment, a change in thethickness T of the entire free layer 34 and the thickness of the entireMR element 30 can be reduced.

Next, other effects of the present example embodiment will be described.In the present example embodiment, the thickness T of the free layer 34at a given position on the first surface 34 a decreases as the angle θat the position on the first inclined portion SL1 closest to the givenposition increases. Such a relationship between the thickness T and theangle θ can be achieved by forming the layered film 30P using aso-called non-conformal film formation apparatus such as a magnetronsputtering apparatus.

In the present example embodiment, in particular, the thickness T1 atthe first edge Ed1 is smaller than the thickness T2 at the second edgeEd2 in a given cross section S. Therefore, according to the presentexample embodiment, the concentration of magnetic charges at and nearthe first edge Ed1 of the free layer 34 can thus be reduced.

The effect of reducing the concentration of magnetic charges will bedescribed in detail below by comparison with an MR element 230 accordingto a comparative example. The MR element 230 of the comparative examplewill initially be described with reference to FIG. 14. FIG. 14 is anexplanatory diagram for describing magnetic charges on the MR element230 of the comparative example. FIG. 14 shows a cross sectioncorresponding to the cross section S. Like the MR element 30 accordingto the present example embodiment, the MR element 230 according to thecomparative example includes a magnetization pinned layer 232, a spacerlayer 233, a free layer 234, and a not-shown underlayer and cap layer.

The MR element 230 of the comparative example is located on a flatsurface parallel to the bottom surface 60 b of the support member 60.Like the MR element 30 according to the present example embodiment, theMR element 230 is patterned to a shape that is long in the X direction.This gives the free layer 234 magnetic shape anisotropy where thedirection of the easy axis of magnetization is parallel to the Xdirection.

The free layer 234 includes a first surface 234 a located at an end inthe Z direction, a second surface 234 b opposite to the first surface234 a, and an outer peripheral surface connecting the first surface 234a and the second surface 234 b. Both the first and second surfaces 234 aand 234 b are flat surfaces parallel to the bottom surface 60 b. Thefirst and second surfaces 234 a and 234 b each have a shape that is longin the X direction. The first surface 234 a has a first edge Ed11 and asecond edge Ed12 located at both ends in the lateral direction of thefirst surface 234 a, i.e., a direction parallel to the Y direction. Inparticular, in the comparative example, the first edge Ed11 is an edgelocated at the end of the first surface 234 a in the −Y direction. Thesecond edge Ed12 is an edge located at the end of the first surface 234a in the Y direction.

If an external magnetic field is applied to the MR element 230, thedirection of the magnetic moment inside the free layer 234 rotatesdepending on the direction and strength of the external magnetic field.As a result, the direction of the magnetization of the free layer 234rotates. Here, magnetic charges occur on the outer peripheral surface ofthe free layer 234.

Now, suppose that an external magnetic field in the Y direction isapplied to the MR element 230. If the external magnetic field in the Ydirection is applied, positive magnetic charges concentrate at a portionof the outer peripheral surface of the free layer 234 near the secondedge Ed12, and negative magnetic charges concentrate at a portion of theouter peripheral surface of the free layer 234 near the first edge Ed11.In FIG. 14, the symbols “+” represent positive magnetic charges, and thesymbols “−” negative magnetic charges. A demagnetizing field in the −Ydirection occurs in the free layer 234 due to such magnetic charges. Thestrength of the demagnetizing field is higher as it is closer to themagnetic charges. The strength of the demagnetizing field in theportions of the free layer 234 near the first and second edges Ed11 andEd12 is therefore high. The strength of the demagnetizing field in themidsection of the free layer 234 is low.

If no external magnetic field is applied, the direction of themagnetization of the free layer 234 and the direction of the magneticmoment in the free layer 234 are parallel to the X direction. If thestrength of the external magnetic field is low, the direction of themagnetic moment in the midsection of the free layer 234 starts to rotatetoward the Y direction. On the other hand, the direction of the magneticmoment in the portions of the free layer 234 near the first and secondedges Ed11 and Ed12 does not rotate or hardly rotates.

If the strength of the external magnetic field becomes high to a certainextent, the direction of the magnetic moment in the midsection of thefree layer 234 becomes the same or substantially the same as the Ydirection. Meanwhile, the direction of the magnetic moment in theportions of the free layer 234 near the first and second edges Ed11 andEd12 starts to rotate toward the Y direction. If the strength of theexternal magnetic field becomes even higher, the direction of themagnetic moment in the portions of the free layer 234 near the first andsecond edges Ed11 and Ed12 also becomes the same or substantially thesame as the Y direction.

As described above, in the MR element 230 of the comparative example,the direction of the magnetic moment in the entire free layer 234 doesnot change uniformly because of the demagnetizing field. As a result,the magnetization of the free layer 234 changes nonlinearly with respectto a change in the strength of the external magnetic field.Consequently, a detection signal generated by a magnetic sensorincluding the MR element 230 of the comparative example changesnonlinearly with respect to a change in the strength of the externalmagnetic field.

Next, magnetic charges on the MR element 30 according to the presentexample embodiment will be described. FIG. 15 is an explanatory diagramfor describing magnetic charges on the MR element 30. FIG. 15 shows across section corresponding to the cross section S. In FIG. 15, thesymbols “+” represent positive magnetic charges, and the symbols “−”negative magnetic charges.

In the MR element 30 according to the present example embodiment, thethickness T1 at the first edge Ed1 is smaller than the thickness T2 atthe second edge Ed2. Now, suppose that an external magnetic field in theY direction is applied to the MR element 30. In such a case, positivemagnetic charges concentrate at a portion of the outer peripheralsurface of the free layer 34 near the second edge Ed2 as in thecomparative example. By contrast, negative magnetic charges do notconcentrate at a portion of the outer peripheral surface of the freelayer 34 near the first edge Ed1 but are distributed even over the firstsurface 34 a. This reduces a difference between the strength of thedemagnetizing field at the portion of the free layer 34 near the firstedge Ed1 and that of the demagnetizing field in the midsection of thefree layer 34. As the difference decreases, the direction of themagnetic moment at the portion of the free layer 34 near the first edgeEd1 rotates more similarly to that of the magnetic moment in themidsection of the free layer 34. According to the present exampleembodiment, the magnetization of the free layer 34 can thus be preventedfrom changing nonlinearly with respect to a change in the strength ofthe external magnetic field. As a result, according to the presentexample embodiment, the range where the detection signal generated bythe magnetic sensor 1 change linearly can be expanded.

To reduce variations in the thickness of the MR element 30 due tovariations in the manufacturing process, the curvature k of the entirefirst inclined portion SL1 can be reduced. This, however, reduces adifference between the first angle θ1 and the second angle θ2, andreduces a difference between the thickness T1 at the first edge Ed1 andthe thickness T2 at the second edge Ed2. In particular, if the entirefirst inclined portion SL1 has a curvature k of 0, i.e., the entirefirst inclined portion SL1 is a flat surface, the first angle θ1 and thesecond angle θ2 are the same, and the thickness T1 at the first edge Ed1and the thickness T2 at the second edge Ed2 are the same. Thisannihilates the effect of reducing the concentration of magnetic chargesat and near the first edge Ed1.

By contrast, according to the present example embodiment, the absolutevalue of the curvature k2 of the first inclined portion SL1 at thesecond position P2 where the angle θ is relatively small is maderelatively large. According to the present example embodiment, thedifference between the first angle θ1 and the second angle θ2 is therebyincreased to increase the difference between the thickness T1 at thefirst edge Ed1 and the thickness T2 at the second edge Ed2. According tothe present example embodiment, the concentration of magnetic charges atand near the first edge Ed1 of the free layer 34 can thus be reducedwhile reducing a change in the thickness T1 at the first edge Ed1 due tovariations in the manufacturing process.

The effects of the present example embodiment have so far been describedby using the MR element 30 provided on the first inclined portion SL1 asan example. However, the foregoing description also applies to the MRelement 30 provided on the second inclined portion SL2 since the firstinclined portion SL1 and the second inclined portion SL2 have asymmetrical shape.

Modification Example

Next, a modification example of the MR element 30 will be described withreference to FIG. 16. In the modification example, the MR element 30 isan anisotropic magnetoresistive (AMR) element. In the modificationexample, the MR element 30 includes a magnetic layer 36 given magneticanisotropy, instead of the magnetization pinned layer 32, the spacerlayer 33, and the free layer 34 shown in FIG. 6. The magnetic layer 36has a magnetization whose direction is variable depending on thedirection of the external magnetic field. As described above, the MRelement 30 is patterned to a shape that is long in the X direction. Thisgives the magnetic layer 36 magnetic shape anisotropy where thedirection of the easy axis of magnetization is parallel to the Xdirection.

The magnetic layer 36 has a first surface 36 a having a shape that islong in the X direction, a second surface 36 b opposite to the firstsurface 36 a, and an outer peripheral surface connecting the firstsurface 36 a and the second surface 36 b. The description of the shapeof the MR element 30 with reference to FIGS. 6 and 7 also applies to themodification example. The description of the shape of the MR element 30applies to the shape of that in the modification example, with the freelayer 34, the first surface 34 a, and the second surface 34 b in thedescription replaced with the magnetic layer 36, the first surface 36 a,and the second surface 36 b, respectively.

Second Example Embodiment

A second example embodiment of the technology will now be described.Initially, a configuration of a magnetic sensor according to the presentexample embodiment will be described with reference to FIG. 17. FIG. 17is a cross-sectional view showing a part of the magnetic sensoraccording to the present example embodiment.

A configuration of the magnetic sensor 101 according to the presentexample embodiment differs from that of the magnetic sensor 1 accordingto the first example embodiment in the following respect. The magneticsensor 101 according to the present example embodiment includes MRelements 130 instead of the MR elements 30 according to the firstexample embodiment. FIG. 17 shows a cross section parallel to the YZplane and intersecting an MR element 130.

The opposed surface 60 a of the support member 60 includes at least onecurved portion 60 a 3 not parallel to the bottom surface 60 b, insteadof the curved portion 60 a 2 according to the first example embodiment.As shown in FIG. 17, the curved portion 60 a 3 is a concave surfacerecessed toward the bottom surface 60 b. As will be described below, theopposed surface 60 a includes inclined portions that are a part of theconcave surface (curved portion 60 a 3). The curved portion 60 a 3 has acurved shape (arch shape) curved to be recessed toward the bottomsurface 60 b (−Z direction) in a given cross section parallel to the YZplane. In the given cross section parallel to the YZ plane, the distancefrom the bottom surface 60 b to the curved portion 60 a 3 is thesmallest at the center of the curved portion 60 a 3 in a directionparallel to the Y direction (hereinafter, referred to simply as thecenter of the curved portion 60 a 3).

The curved portion 60 a 3 extends along the X direction. The overallshape of the curved portion 60 a 3 is a semicylindrical curved surfaceformed by moving the curved shape shown in FIG. 17 along the Xdirection. The insulating layer 62 of the support member 60 has across-sectional shape such that the curved portion 60 a 3 is formed inthe opposed surface 60 a. Specifically, the insulating layer 62 has across-sectional shape recessed in the −Z direction in a given crosssection parallel to the YZ plane.

A portion of the curved portion 60 a 3 from an edge at the end of thecurved portion 60 a 3 in the Y direction to the center of the curvedportion 60 a 3 will be referred to as a first inclined portion and bedenoted by the symbol SL11. A portion of the curved portion 60 a 3 froman edge at the end of the curved portion 60 a 3 in the −Y direction tothe center of the curved portion 60 a 3 will be referred to as a secondinclined portion and be denoted by the symbol SL12. Both the first andsecond inclined portions SL11 and SL12 are inclined relative to thebottom surface 60 b. In the present example embodiment, the entire MRelement 130 is located on the first inclined portion SL11 or the secondinclined portion SL12. FIG. 17 shows how the MR element 130 is locatedon the first inclined portion SL11.

The MR element 130 has a shape that is long in the X direction. The MRelement 130 has a rectangular planar shape. As employed herein, thelateral direction of the MR element 130 will be referred to as the widthdirection of the MR element 130 or simply as the width direction. The MRelement 130 has a bottom surface 130 a, a top surface 130 b, a firstedge 130 c, a second edge 130 d, a third edge, and a fourth edge. Thebottom surface 130 a is opposed to the curved portion 60 a 3. The topsurface 130 b is located opposite the bottom surface 130 a. The firstand second edges 130 c and 130 d are located at both ends in the widthdirection. The third and fourth edges are located at both ends in thelongitudinal direction. The dimension of the MR element 130 in the widthdirection is constant or substantially constant regardless of theposition in the X direction.

The MR element 130 may be a spin-valve MR element or an AMR element. Thefollowing description will be given by using the case where the MRelement 130 is a spin-valve MR element as an example. Like the MRelement 30 shown in FIG. 6 of the first example embodiment, the MRelement 130 includes an underlayer 31, a magnetization pinned layer 32,a spacer layer 33, a free layer 34, and a cap layer 35. The free layer34 has magnetic shape anisotropy where the direction of the easy axis ofmagnetization is parallel to the X direction.

Next, the inclined portions and the MR elements 130 will be described indetail with reference to FIG. 18. The following description will begiven by using the first inclined portion SL11 as an example. FIG. 18 isan explanatory diagram for describing the shape of the first inclinedportion SL11. FIG. 18 is an enlarged view of a part of the cross sectionshown in FIG. 17. In FIG. 18, the underlayer 31 and the cap layer 35 ofthe MR element 130 are omitted.

A cross section intersecting the MR element 130 and being perpendicularto the bottom surface 60 b of the support member 60 will be denoted bythe symbol S. To describe the shape of the first inclined portion SL11,a first position P11, a second position P12, a third position P13, and afourth position P14 on the first inclined portion SL11 in a given crosssection S will be defined as follows. The first position P11 is aposition where the first inclined portion SL11 is inclined relative tothe bottom surface 60 b at a first angle θ11. The second position P12 isa position where the first inclined portion SL11 is inclined relative tothe bottom surface 60 b at a second angle θ12 smaller than the firstangle θ11. In the present example embodiment, in particular, the firstposition P11 is farther from the bottom surface 60 b than is the secondposition P12.

The third position P13 is the position on the first inclined portionSL11 closest to the bottom surface 60 b. Specifically, the thirdposition P13 is located at the border between the first inclined portionSL11 and the second inclined portion SL12, i.e., the center of thecurved portion 60 a 3. The fourth position P14 is the position on thefirst inclined portion SL11 farthest from the bottom surface 60 b.Specifically, the fourth position P14 is located at the border betweenthe curved portion 60 a 3 and the flat portion 60 a 1. The firstposition P11 and the second position P12 fall within the range from thethird position P13 to the fourth position P14.

Both the angle that the first inclined portion SL11 forms with thebottom surface 60 b at the third position P13 and the angle that thefirst inclined portion SL11 forms with the bottom surface 60 b at thefourth position P14 are 0°. Both the first and second angles θ11 and θ12are greater than 0° and less than 90°.

The outline of the first inclined portion SL11 in a given cross sectionS includes a plurality of curves where each curve has a differentcurvature. The absolute value of a curvature k11 of the first inclinedportion SL11 at the first position P11 is less than that of a curvaturek12 of the first inclined portion SL11 at the second position P12.

In FIG. 18, the circular arc denoted by the symbol C11 represents a partof a circle approximating the first inclined portion SL11 at the firstposition P11, i.e., a first circle of curvature. The circular arcdenoted by the symbol C12 represents a part of a circle approximatingthe first inclined portion SL11 at the second position P12, i.e., asecond circle of curvature. As shown in FIG. 18, the first circle ofcurvature (symbol C11) has a radius greater than that of the secondcircle of curvature (symbol C12).

The MR element 130 is provided on the first inclined portion SL11 sothat the first edge 130 c is located above the first position P11 in agiven cross section S. Further, in the present example embodiment, theMR element 130 is provided on the first inclined portion SL11 so thatthe second edge 130 d is located above the second position P12 in thegiven cross section S.

As described in the first example embodiment, the free layer 34 has afirst surface 34 a, a second surface 34 b, and an outer peripheralsurface. The first surface 34 a has a first edge Ed1 and a second edgeEd2 located at both lateral ends of the first surface 34 a. The firstedge Ed1 is located at the first edge 130 c of the MR element 130. Thesecond edge Ed2 is located at the second edge 130 d of the MR element130.

The relationship between the inclination angle θ1 at the first edge Ed1and the inclination angle θ2 at the second edge Ed2 in a given crosssection S is the same as in the first example embodiment. Therelationship between the thickness T1 at the first edge Ed1 and thethickness T2 at the second edge Ed2 in a given cross section S is alsothe same as in the first example embodiment. For the sake ofconvenience, an imaginary surface is assumed by extending the secondsurface 34 b along the curved portion 60 a 3, and the thickness T1 isdefined as the distance between the first surface 34 a and the imaginarysurface in the direction perpendicular to the first surface 34 a.

The foregoing description has been given by using the first inclinedportion SL11 as an example. The first inclined portion SL11 and thesecond inclined portion SL12 have a shape symmetrical or substantiallysymmetrical about the XZ plane including the center of the curvedportion 60 a 3. The foregoing description of the first inclined portionSL11 therefore also applies to the second inclined portion SL12. Theforegoing description of the MR element 130 also applies to the MRelement 130 provided on the second inclined portion SL12.

The configuration, operation and effects of the present exampleembodiment are otherwise the same as those of the first exampleembodiment.

The technology is not limited to the foregoing example embodiments, andvarious modification examples may be made thereto. For example, thenumber and arrangement of MR elements and the number and arrangement ofcurved portions are not limited to those described in the exampleembodiments, and may be freely chosen as long as the requirements setforth in the claims are satisfied.

The first and second surfaces 34 a and 34 b of the free layer 34according to the technology may each have a shape long in a directionintersecting a given cross section S, not necessarily in the directionparallel to the X direction.

The second edge of the MR element according to the technology may belocated on the flat portion 60 a 1 or a part of the curved portionparallel to the bottom surface 60 b.

Obviously, various modification examples and variations of thetechnology are possible in the light of the above teachings. Thus, it isto be understood that, within the scope of the appended claims andequivalents thereof, the technology may be practiced in otherembodiments than the foregoing example embodiments.

What is claimed is:
 1. A magnetic sensor comprising: a magnetoresistiveelement whose resistance changes with an external magnetic field; and asupport member configured to support the magnetoresistive element,wherein: the support member has an opposed surface opposed to themagnetoresistive element, and a bottom surface formed of a flat surfacelocated opposite the opposed surface; the opposed surface includes aninclined portion inclined relative to the bottom surface; in a specificcross section of the magnetic sensor perpendicular to the bottomsurface, the inclined portion is inclined relative to the bottom surfaceat a first angle at a first position on the inclined portion, andinclined relative to the bottom surface at a second angle at a secondposition on the inclined portion, the second angle being smaller thanthe first angle; an absolute value of a curvature of the inclinedportion at the first position is less than an absolute value of acurvature of the inclined portion at the second position; and themagnetoresistive element has a first edge and a second edge located atboth ends of the magnetoresistive element in a width direction, and isprovided on the inclined portion so that the first edge is located abovethe first position in the cross section.
 2. The magnetic sensoraccording to claim 1, wherein the magnetoresistive element is providedon the inclined portion so that the second edge is located above thesecond position in the cross section.
 3. The magnetic sensor accordingto claim 1, wherein the first position and the second position fallwithin a range from a third position on the inclined portion closest tothe bottom surface in the cross section to a fourth position on theinclined portion farthest from the bottom surface in the cross section.4. The magnetic sensor according to claim 3, wherein: the inclinedportion is inclined relative to the bottom surface so that the firstangle is a maximum and the second angle is a minimum within a range fromthe first position to the second position; and the absolute value of thecurvature of the inclined portion is minimized at the first position andmaximized at a predetermined position other than the first positionwithin the range from the first position to the second position.
 5. Themagnetic sensor according to claim 1, wherein: the opposed surfaceincludes a convex surface protruding in a direction away from the bottomsurface; and the inclined portion is a part of the convex surface. 6.The magnetic sensor according to claim 1, wherein: the opposed surfaceincludes a concave surface recessed toward the bottom surface; and theinclined portion is a part of the concave surface.
 7. The magneticsensor according to claim 1, wherein: the magnetoresistive elementincludes a magnetic layer having a magnetization whose direction isvariable depending on the external magnetic field; the magnetic layerhas a first surface and a second surface located opposite the firstsurface, and has a thickness that is a dimension in a directionperpendicular to the first surface of the magnetic layer; and thethickness at the first edge is smaller than the thickness at the secondedge.
 8. The magnetic sensor according to claim 7, wherein the thicknessdecreases toward the first edge from the second edge.
 9. The magneticsensor according to claim 7, wherein the first surface and the secondsurface each have a shape long in a direction intersecting the crosssection.